Method for producing an electrode of a field-effect-controllable semiconductor component and field-effect-controllable semiconductor component

ABSTRACT

A field-effect-controllable semiconductor component and a method for fabricating an electrode of the component includes a semiconductor body having a first zone of a first conduction type, a second zone of a second conduction type disposed above the first zone, and at least one trench extending into the semiconductor body in a vertical direction through the second zone, applying a first insulation layer at least in a region of the second zone in the trench, applying a first layer of electrode material to the semiconductor body, applying an intermediate layer to the first layer, applying a second layer of electrode material to the intermediate layer, removing a portion of the second layer and of the intermediate layer to leave the intermediate layer and the second layer at least partly in the trench, and patterning the first layer.

DESCRIPTION

[0001] Method for fabricating an electrode of afield-effect-controllable semiconductor component andfield-effect-controllable semiconductor component

[0002] The present invention relates to a method for fabricating anelectrode of a field-effect-controllable semiconductor component and toa field-effect-controllable semiconductor component.

[0003] In the course of an increasing integration density in integratedcircuits, endeavors are made to integrate power transistors, inparticular power field-effect transistors, and their associated drivecircuit or drive logic in a semiconductor body.

[0004] Power transistors are usually transistors of vertical design,i.e. source and drain terminals of the transistors are situated onopposite sides of the semiconductor body, in which case the gateelectrode can be arranged in a trench in a manner insulated from thesemiconductor body. In components of this type, a conductive channelruns through the semiconductor body in the vertical direction. Bycontrast, components, in particular transistors, of the drive circuitare usually designed as lateral components, i.e. the terminals of thesetransistors are situated at one side of the semiconductor body and aconductive channel in the case of these transistors usually forms in thelateral direction in the semiconductor body. The different geometricalconstruction of the power transistors and of the transistors of thedrive logic means that different method steps are required to fabricatethem.

[0005] This does not constitute a problem if the power transistors andthe drive logic are realized in different semiconductor bodies. However,if the power transistors and the components of the drive logic areintended to be integrated in a single semiconductor body, there is aneed to be able to jointly utilize as many method steps as possible forthe power transistor part and the drive logic part. Problems are posedhere in particular by the fabrication of electrodes of the powertransistors and of the transistors of the drive logic.

[0006] In the case of transistors of lateral design, the controlelectrodes, i.e. the gate electrodes in field-effect transistors, arefabricated by depositing an electrode layer onto an insulation layer onthe semiconductor body. In the case of vertical power transistorsdesigned as so-called trench transistors, in which the control electrodeis thus formed in a trench of the semiconductor body, the trench isfilled with an electrode material after the fabrication of an insulationlayer at the trench surface, for this purpose an electrode materialusually being deposited onto the semiconductor body, and hence also intothe trenches. The thickness of the electrode material that is to bedeposited in this case is dependent on the width of the trench which isto be filled. Thus, the thickness of the deposited electrode materialmust approximately correspond to the trench width in order to fill thetrench by deposition of the electrode material and to obtain anapproximately planar surface after etching-back of the electrode layeron the surface of the semiconductor body. In the case of trenches havinga width of 800 nm, it is customary at the present time to deposit anelectrode layer having a thickness of approximately 1 μm. However, anelectrode layer this thick is not suitable for fabricating gateelectrodes of the drive logic, for which a thinner electrode layer hasto be provided.

[0007] It is an aim of the present invention, therefore, to provide amethod for fabricating an electrode of a field-effect-controllablesemiconductor component which can equally be used for fabricating anelectrode of a power transistor and for fabricating an electrode of atransistor of a drive logic.

[0008] This aim is achieved by means of a method in accordance with thefeatures of patent claim 1.

[0009] The subclaims relate to advantageous refinements of the methodaccording to the invention.

[0010] In the method according to the invention, firstly provision ismade of a semiconductor body having a first zone of a first conductiontype and, arranged above the latter, a second zone of a secondconduction type, and at least one trench which extends into thesemiconductor body in the vertical direction through the second zone.The fabrication of such a semiconductor body with the features mentionedis adequately known from methods for fabricating power transistors.Afterward, a first insulation layer is fabricated at least in the regionof the second zone in the at least one trench. This insulation layer maybe, in particular, a layer made of an oxide of the semiconductormaterial which is produced by means of a thermal method. Afterward, alayer made of electrode material is deposited onto the semiconductorbody and hence also in the at least one trench. In a next method step,an intermediate layer is applied to said first layer made of electrodematerial, on which intermediate layer a second layer made of electrodematerial is then applied. The second layer made of electrode materialand the intermediate layer are then removed above the semiconductorbody, the intermediate layer and the second layer made of electrodematerial at least partly remaining in the trench. Afterward, the firstlayer made of electrode material is patterned in order to form theelectrode.

[0011] The present method, in which an electrode of afield-effect-controllable semiconductor component is fabricated bydeposition of a first electrode layer, an intermediate layer and asecond electrode layer, is suitable both for fabricating a controlelectrode of a power transistor in a trench of the semiconductor bodyand for fabricating a control electrode—arranged on a surface of thesemiconductor body—of a transistor of lateral design. In this case, thethickness of the first electrode layer is chosen in such a way that itis suitable for forming a control electrode, or gate electrode, of alateral transistor of the drive logic. In this case, this electrodelayer is usually so thin that the trenches of the later power transistorare not completely filled. In the method according to the invention, thetrenches are filled by means of the second electrode layer which isdeposited onto the intermediate layer and whose thickness is chosen insuch a way that the trenches are completely filled. After the removal ofthe second electrode layer and the intermediate layer from regions abovethe semiconductor body, only the first thinner electrode layer remainson the semiconductor body for the as purpose of forming controlelectrodes of the drive logic, while the trenches are completely filledby the first thinner electrode layer and the second electrode layerapplied above the latter. In the method according to the invention, theintermediate layer serves in particular as a stop layer during anetching operation in which the second electrode layer is removed fromthe surface of the semiconductor body. The intermediate layer issubsequently removed in a further method step.

[0012] In accordance with one embodiment of the invention, it isprovided that before the fabrication of the first insulation layer inthe at least one trench, a second insulation layer is fabricated whichat least partly covers the surface of the at least one trench. Thissecond insulation layer is thicker than the first insulation layer andcovers the surface of the at least one trench preferably below thesecond zone. The thickness of this second insulation layer is preferablychosen in such a way that, after the fabrication of the first insulationlayer in the trench in the region of the second zones and the depositionof the first layer made of electrode material, the trench is completelyfilled with electrode material where the second insulation layer isapplied.

[0013] As already mentioned, in vertical power transistors, a conductivechannel runs in the vertical direction in the semiconductor body. Intransistors it is known to arrange so-called field plates along theconductive channel, the use of which field plates makes it possible toachieve a lower resistance of the transistor in the on state with abreakdown voltage that remains the same or is increased. In this case,that section of the first electrode layer which is arranged on thesecond insulation layer in the region of the first zone of thesemiconductor body in the trench acts as such a field plate.

[0014] In accordance with a further embodiment of the invention, it isprovided that the semiconductor body has at least two trenches, in whichcase, before the method step for fabricating the first electrode layerin one of the trenches, a second insulation layer is fabricated whichcovers the surface of the trench in the region of the first zone andsecond zone of the semiconductor body. In this case, the thickness ofthis second insulation layer is chosen in such a way that, after thedeposition of the first layer made of electrode material, said trench iscompletely filled with electrode material. It is known to realize powertransistors from a plurality of identically constructed cells which areinterconnected. The trench which is completely filled with the secondinsulation layer and the first layer made of electrode material in thiscase serves for laterally delimiting the cell array, the section of thefirst layer made of electrode material in this trench acting as a fieldplate. This field plate is usually connected to the same potential asthe control electrodes in the rest of the trenches, the secondinsulation layer being too thick to allow the field plate to act as agate electrode.

[0015] The present invention furthermore relates to afield-effect-controllable semiconductor component in accordance withclaim 11. Claims 12 and 13 relate to advantageous refinements of thissemiconductor component according to the invention.

[0016] The present invention is explained below using exemplaryembodiments with reference to figures, in which:

[0017]FIGS. 1A to 1H show method steps for fabricating an electrode of afield-effect-controllable semiconductor component in accordance with amethod according to a first embodiment;

[0018]FIGS. 2A to 2H show method steps for fabricating an electrode of afield-effect-controllable semiconductor component of a second embodimentof the invention in accordance with a method according to a secondembodiment;

[0019]FIG. 3 shows a cross section through a semiconductor componentaccording to the invention for illustrating a possibility for contactconnection of a first and second electrode in a trench of asemiconductor body.

[0020] In the figures, unless specified otherwise, identical referencesymbols designate identical regions with the same meaning.

[0021]FIGS. 1A to 1H illustrate a method according to the invention forfabricating an electrode of a field-effect-controllable semiconductorcomponent.

[0022] As is illustrated in FIG. 1A, a semiconductor body 10 is providedin this case in a first method step, which semiconductor body has afirst zone 12 of a first conduction type, an n-conducting zone in thepresent case, and, lying above the latter, a zone of a second conductiontype, a p-doped zone in the present case. The semiconductor body 10additionally has at least one trench which extends into thesemiconductor body 10 in the vertical direction of the semiconductorbody through the second zone 14, two trenches 20A, 20B being illustratedin the exemplary embodiment in FIG. 1A. In addition, an insulation layer30, for example an oxide made of semiconductor material, is applied to afront side 101 of the semiconductor body 10.

[0023]FIG. 1A shows two sections I and II of the same semiconductor body10, which are arranged spaced apart from one another in the lateraldirection of the semiconductor body 10. The part designated by I, whichis referred to as power transistor part hereinafter, in this case servesfor fabricating a vertical power transistor. The part designated by II,which is referred to as drive logic part hereinafter, in this caseserves for fabricating components, in particular transistors, for adrive logic of the power transistor.

[0024] By way of example, a p-doped well 16 in the n-doped region 12 ofthe semiconductor body 10 is illustrated in the drive logic part II,which well is laterally terminated by means of heavily p-doped sidewalls17, 18. In the present example, the p-doped well 16 shown in the drivepart in FIG. 1A serves for fabricating an n-conducting field-effecttransistor of lateral design. An n-doped zone 19 formed in the p-dopedwell 16 below a surface of the semiconductor body 10 serves as a laterdrift path of the transistor. An insulation layer 32 is applied to thesurface of the semiconductor body 10 in the drive logic part II, whichinsulation layer becomes thicker towards the edges of the p-doped well16.

[0025] After the provision of the semiconductor arrangement illustratedin FIG. 1A, in a next method step, whose result is illustrated in FIG.1B, a first insulation layer 34A, 34B is fabricated in the trenches 20A,20B. This first insulation layer 34A, 34B is preferably fabricated bymeans of a thermal method during which the semiconductor body is heated,so that the semiconductor material oxidizes at the surface of thetrenches 20A, 20B. As a result of this thermal step, the thickness ofthe insulation layer 30 applied to the front side 101 of thesemiconductor body 10 in the power transistor part I and the thicknessof the insulation layer 32 in the drive logic part II may also increase,but this is not illustrated in FIG. 1B. The insulation layers 34A, 34Bform the gate insulation for the later gate electrodes.

[0026] In a next method step, whose result is illustrated in FIG. 1C, afirst layer 40 made of electrode material is applied to thesemiconductor body 10. If silicon is used as semiconductor material,polysilicon is preferably deposited onto the semiconductor body 10 forthis purpose. The first layer 40 made of electrode material is appliedover the entire surface of the semiconductor body 10, so that the firstlayer 40 made of electrode material covers the surface of the trenches20A, 20B and the regions of the front side 101 of the semiconductor body10 and, in particular, the semiconductor body in the region of the drivelogic part II. In this case, the thickness of the first layer 40 made ofelectrode material is chosen in such a way that it is suitable forfabricating control electrodes, or gate electrodes, of transistors inthe drive logic part.

[0027] In subsequent method steps, whose result is illustrated in FIG.1D, firstly an intermediate layer 50 is applied to the first layer 40made of electrode material and then a second layer 60 made of electrodematerial is applied to the intermediate layer 50. In this case, thethickness of the applied second layer 60 made of electrode material ischosen in such a way that the trenches 20A, 20B are completely filled bythe second layer 60 made of electrode material. The second layer 60 madeof electrode material is preferably composed of the same material as thefirst layer 40 made of electrode material.

[0028] In subsequent method steps, whose result is illustrated in FIG.1E, the second layer 60 made of electrode material and the intermediatelayer 50 are removed above the surface of the semiconductor body 10,sections 50A, 50B of the intermediate layer and sections 60A, 60B of thesecond layer made of electrode material remaining in the trenches 20A,20B, in order to fill the trenches. The second layer 60 made ofelectrode material and the intermediate layer 50 are preferably removedin a plurality of method steps, the second layer 60 made of electrodematerial being removed in a first method step, for example by etching.In this case, the intermediate layer 50 serves as a stop layer which isnot removed by the etching method. If silicon is used as semiconductormaterial, the intermediate layer is preferably composed of tetraethylorthosilicate (TEOS). This intermediate layer 50 is then removed in anext method step, in order to attain the arrangement illustrated in FIG.1E. The electrode layer 40 remaining above the drive logic part IIretains its original thickness during the removal of the secondelectrode layer 60 and the intermediate layer 50. In this case, thethickness of this first electrode layer 40 is chosen in such a way thatit is suitable for fabricating electrodes of the lateral transistors ofthe drive logic part II. The thickness of this first electrode layer 40is usually too small to enable the trenches 20A, 20B to be completelyfilled. In the method according to the invention, therefore, thetrenches 20A, 20B are completely filled by the second electrode layer60, or the parts 60A, 60B thereof which remain after the etching-backprocess.

[0029]FIG. 1F shows the arrangement in accordance with FIG. 1E after anext method step in which a photomask 170 is applied above the drivelogic part II. This photomask 170 has cutouts 171, 172, 173, 174, and,in a next method step, whose result is illustrated in FIG. 1G, the firstlayer 40 made of electrode material is removed from the regions of thesemiconductor body 10 which are not covered by the photomask 170. In theillustration in accordance with FIG. 1G, the photomask 170 has alreadybeen removed after the performance of the step for partly removing thefirst electrode layer 40, which is preferably effected by means of anetching method.

[0030] After the partial removal of the first layer made of electrodematerial, after which sections 40C, 40D, 40E, 40F, 40G of the firstlayer made of electrode material remain on the surface, there lie freein the power transistor part I and in the drive logic part regions ofthe surface of the semiconductor body which are covered only by the thininsulation layer 30 in the power transistor part I and, respectively, bythin sections of the insulation layer 32 in the drive logic part II.N-doped zones 70, 72, 74 are then produced in these regions of thesemiconductor body 10, for example by means of a diffusion method. Inthe region of the drive logic part II, these n-doped zones 72, 74 areformed in a well-like manner in the regions of the front side of thesemiconductor body 10 which are left free by the remaining sections 40C,40D, 40E, 40F, 40G of the first layer made of electrode material. In thepower transistor part of the semiconductor body 10, the n-doped zone 70extends between the trenches 20A, 20B below the front side of thesemiconductor body 10.

[0031] The result of these last-mentioned method steps is illustrated inFIG. 1H. After the indiffusion of the n-doped zones, a furtherinsulation layer 80 is deposited and patterned by means of known methodsteps, this insulation layer 80 leaving free sections of the surface ofthe semiconductor body 10 or of the remaining sections 40D, 40F of theelectrode layer in order that these regions are contact-connected bymeans of subsequently applied electrodes. In the region of the powertransistor part I, the insulation layer 80 leaves free regions of thesurface of the semiconductor body 10, a further electrode, for examplemade of metal, subsequently being fabricated, which electrodecontact-connects the n-doped regions 70 between trenches 20A, 20B. Thiselectrode 90 serves as source electrode S1 of the power transistor andis preferably designed in such a way that it short-circuits the n-dopedzones 70 and the p-doped second zone 14. In the power transistor part I,the first n-doped zone 12 of the semiconductor body 10 serves as drainzone D1 and the combination—formed in the trenches 20A, 20B—comprisingfirst electrode layer 40A, 40B and second electrode layer 60A, 60B,which are preferably connected to the same potential, serves as gateelectrode of the power transistor. The first electrode layer 40A, 40B isformed as a result of the fabrication method in the trenches 20A, 20Bbetween the second electrode layer 60A, 60B and the sidewalls of thetrenches. The first electrode layer 40A, 40B thus partly surrounds thesecond electrode layer 60A, 60B in the trenches 20A, 20B. When a drivepotential is applied to the gate electrode 40A, 60A, 40B, 60B, aconductive channel forms in the p-doped channel zone 14 along theinsulation layer 34A, 34B of the trenches, as a result of which a chargeflow arises when a voltage is applied between the drain zone D1 and thesource electrode S1.

[0032] The gate electrodes 40A, 60A, 40B, 60B are connected to oneanother and to a common drive potential in a manner that is notspecifically illustrated in FIG. 1H.

[0033] For this purpose, as is illustrated in FIG. 3, provision is madeof, for example, a further trench 200 in the semiconductor body 10,which runs perpendicularly to the trenches 20A, 20B and in which theconnection for the gate electrodes is provided. FIG. 3 shows a crosssection through the second zone 14 in the power part I in plan view. Thereference symbol 210 in this case designates an electrode which connectsthe gate electrodes 40A, 60A, 40B, 60B to one another and is insulatedfrom the semiconductor body 10 by means of an insulation layer 220.

[0034] In the drive logic part II in accordance with FIG. 1H, atransistor of lateral design is illustrated as a representative of theentire drive logic. In this transistor, the n-doped zone 74 serves assource zone, which is contact-connected by means of a source electrode96, S2 which short-circuits the n-doped zone 77 and the p-doped well 16surrounding the n-doped zone 74. In the n-doped zone 19, a heavilyn-doped zone 72 is formed which serves as drain zone and iscontact-connected by means of a drain zone D2, 92. A section 40F of theelectrode layer serves as gate electrode, which is insulated from thesemiconductor body 10 by means of the insulation layer 32 and extendsfrom the n-doped zone 74 as far as the n-doped zone 19. This section 40Fof the electrode layer is contact-connected by an electrode 94, G2, aconductive channel forming in the lateral direction in the semiconductorbody 10 when a drive potential is applied to said gate electrode, sothat a charge flow arises between the drain zone 72 and the source zone74 when a voltage is applied between the drain electrode D2 and thesource electrode S2.

[0035] The fabrication of the last-described n-doped zones, of thefurther insulation layer and of the gate electrodes is adequately knownfrom methods for fabricating power transistors and from methods forfabricating lateral transistors; a detailed description of these methodsteps can therefore be dispensed with.

[0036]FIGS. 2A to 2H illustrate a further method for fabricating anelectrode of a field-effect-controllable semiconductor component. Inthis case, as in the method illustrated in FIG. 1, firstly asemiconductor body 10 is provided, which, in the exemplary embodiment,has an n-doped first zone 12 and a p-doped second zone 14 lying abovethe latter. In the semiconductor body 10, trenches 22A, 22B are formedin the region of the power transistor part II, said trenches extendinginto the semiconductor body 10 in the vertical direction through thesecond zone 14. Whereas the trenches 20A, 20B end just below the secondzone 14 in the case of the method illustrated in FIG. 1, the trenches22A, 22B extend further into the semiconductor body in the case of theexemplary embodiment in accordance with FIG. 2A. An insulation layer 30is applied to the surface of the semiconductor body 10 in the region ofthe power transistor part I and an insulation layer 32 is applied tosaid surface in the region of the drive logic part II. Situated on theseinsulation layers 30, 32 there is a protective layer 100, preferably anitrite layer.

[0037]FIG. 2B shows the arrangement in accordance with FIG. 2A afterfurther method steps, in which firstly an insulation layer 120, which isillustrated by broken lines in FIG. 2B, is applied to the entiresemiconductor arrangement. In a next method step, a photomask isfabricated, the photomask in the example in accordance with FIG. 2B onlyforming a plug in one of the trenches 22A, which plug extends upward inheight as far as the second zone 14, and the photomask completelycovering a second trench 22B in a region 130B. Afterward, the insulationlayer 120 is removed, for example by means of an etching method, at allpoints where it is not covered by the photomask 130A, 130B. As a result,those regions of the insulation layer 120A, 120B which are drawn usingsolid lines in FIG. 2B remain, which cover the first trench 22A inheight about as far as the second zone 14 and completely cover thesecond trench 22B and, adjoining the second trench 22B, also coverregions of the surface of the semiconductor body 10. The insulationlayer 120 is completely removed above the drive part II. The protectivelayer 100 protects the semiconductor body 10 during the method step inwhich the insulation layer 120 is partly removed. If silicon is used assemiconductor material, the insulation layer 120 is preferably composedof TEOS and is preferably removed by means of an etching method.

[0038] In subsequent method steps, whose result is illustrated in FIG.2C, the photomask 130A, 130B is removed and the protective layer 100 isremoved in the regions which are not covered by the insulation layer120B.

[0039] Afterward, a first insulation layer 34A is fabricated onuncovered regions of the trench 22A in the region of the second zone 14of the semiconductor body 10. As already explained in the method inaccordance with FIG. 1, this insulation layer 34A is fabricated by meansof a thermal step, for example. In this case, the insulation layer 34Ais thinner than the insulation layer 120A, 120B already producedbeforehand. A first layer 40 made of electrode material is subsequentlydeposited over the entire semiconductor body 10. As has already beenexplained with respect to FIG. 1C, this first layer 40 made of electrodematerial completely covers the semiconductor body 10 in the region ofthe drive logic part II. In the exemplary embodiment in accordance withFIG. 2C, the first electrode layer 40 completely fills the trench 22A inthe region of the thick insulation layer 120A. The following methodsteps illustrated in FIGS. 2D to 2H correspond to the method stepsdescribed in FIGS. 1D to 1H, so that reference is made thereto and thesemethod steps are explained with reference to FIGS. 2D to 2H with regardto differences existing between the arrangements according to FIG. 1 andFIG. 2.

[0040] After the deposition of the first layer 40 made of electrodematerial, the intermediate layer 50 is applied to the first electrodelayer 40 and afterward the second layer 60 made of electrode material isapplied to the intermediate layer. In this case, the second layer 60 ischosen in such a way that the trench 22A, which is not yet completelyfilled by the first layer 40, is completely filled with electrodematerial.

[0041] In the next method steps, whose result is illustrated in FIG. 2E,the second electrode layer 60 and the intermediate layer 50 are removedabove the semiconductor body 10, parts of the intermediate layer 50A andof the second electrode layer 60A remaining in the trench 22A in orderto fill the latter. The second electrode layer 60 and the intermediatelayer 50 are removed, as already mentioned, preferably successively in aplurality of method steps.

[0042] In a next method step, whose result is illustrated in FIG. 2F, aphotomask 170 is applied to the first electrode layer 40 in order topattern the latter by means of a subsequent etching method. In theexemplary embodiment in accordance with FIG. 2F, unlike in the methodillustrated in FIG. 1F, the photomask 70 also covers regions of thepower transistor part, namely the first electrode layer 40 above thetrench 22B, in order to protect the first electrode layer 40 from beingremoved in this region.

[0043]FIG. 2G shows the arrangement in accordance with FIG. 2F after theremoval of the first electrode layer 40 in the regions left free by thephotomask 70 and after the removal of the photomask 70.

[0044] In next method steps, whose result is illustrated in FIG. 2H,n-doped zones 70, 72, 74 are produced in the regions of the front sideof the semiconductor body 10 which are not covered by the first layer 40made of electrode material and are only covered by a thin insulationlayer. Afterward, a further insulation layer 80 is fabricated andelectrodes for contact-connecting the semiconductor regions 70, 72, 74and regions of the electrode layer 40F are produced.

[0045] The arrangement of the drive logic part II in accordance withFIG. 2H corresponds to the arrangement in FIG. 1H, so that reference ismade thereto with regard to the construction and function.

[0046] In the power transistor part I, the combination comprising firstelectrode layer 40A and second electrode layer 60A in the trench 22A inthe region of the p-doped second zone 14 forms a gate electrode which isinsulated from the semiconductor body 10 by the first insulation layer34A. That part of the second electrode layer 40A which is formed in thefirst trench 20A in the region of the second insulation layer 120A,which is thicker than the first insulation layer 34A, acts as a fieldplate. In a corresponding manner, the electrode layer 40B in the trench22B acts as a field plate which delimits the power transistor in thelateral direction of the semiconductor body 10. The power transistorpreferably comprises a multiplicity of identically constructedstructures, as are outlined by the dash-dotted line in FIG. 2H. In thiscase, these structures adjoin the structure with the trench 22A towardthe left in the illustration in accordance with FIG. 2H. The field platein the second trench 22B is connected to the gate potential of the gateelectrode 40A.

[0047] The field plate 40B can be electrically connected to the gateelectrode sections 40A, 60A in a manner that is not specificallyillustrated. To that end, by way of example, provision is made of atrench which runs perpendicularly to the trenches 22A, 22B and withwhich the trenches 22A, 22B merge and which is filled for example with aconductive material in order to connect the gate electrode 40A, 60A andthe field plate 40B to one another.

[0048] The field plate 40B in the second trench 22B does not act as agate electrode since the insulation layer 120B between the electrode 40Band the semiconductor body 10 is too thick to bring about a conductivechannel in the second zone 14 when a customary drive potential isapplied.

[0049] As is illustrated in FIG. 2H, the field plate 40B extends beyondthe trench and runs partly above the surface of the semiconductor body10. The gate electrodes 40A, 60A are contact-connected via the fieldplate 40B by a terminal electrode G1 which contact-connects the fieldplate 40B in the part which extends beyond the trench. In this case, theterminal electrode G1 is insulated from the semiconductor body by thecomparatively thick insulation layer 120B, which prevents apunch-through of the drain potential present at the drain zone 12 to theterminal electrode G1 for the gate potential.

[0050] The contact-connection of the gate electrodes 40A, 60A via thefield plate 40B above the trench 22B at the edge of the cell array ofthe power transistor makes it possible to avoid the voltage spikes thatare customary in conventional arrangements in the region of an upperedge of the trenches in which gate electrodes are arranged. In thearrangement according to FIG. 2H, the thick insulation layer 120Baccepts the entire voltage between the terminal electrode G1 for thegate potential and a terminal electrode D1 for the drain potential, thelatter being designed as a metallization layer on the rear side of thesemiconductor body. Further measures, for example suitably doped zones,for preventing a voltage punch-through are thereby unnecessary.

[0051] While the drain zone 12 in the figures described above is alwaysrepresented as an approximately uniformly doped zone, it goes withoutsaying that the drain zone, as is illustrated in FIG. 2H, may have amore heavily doped zone 121 adjoining the drain electrode and a moreweakly doped zone 122 between the more heavily doped zone 121 and thechannel zone 14.

[0052]FIGS. 1H and 2H illustrate a field-effect-controllablesemiconductor component according to the invention in each case in theregion of the power transistor part. In the exemplary embodiments, saidsemiconductor component has a semiconductor body having an n-doped drainzone 12 and an n-doped source zone 70, between which a p-doped channelzone 14 is arranged. In the semiconductor body 10 in which the sourcezone 70, the channel zone 14 and the drain zone 12 are formed, a trench22 extends in the vertical direction of the semiconductor body 10through the source zone 70 and the channel zone 14 right into the drainzone 12. In the trench 22A, a gate electrode is formed which isinsulated from the semiconductor body 10 by means of an insulation layer34A, 34B and is arranged at least in the region of the channel zone 14.Said gate electrode has a first electrode section 40A and a secondelectrode section 60A, between which an intermediate layer 50A isformed.

[0053] In the arrangement according to FIG. 2H, the power transistorfurthermore has a field plate 40B which is arranged in a trench at theedge of the cell array of the power transistor part I and is insulatedfrom the semiconductor body by means of a thick insulation layer 120B,which is thicker than the insulation layer 34A in the region of the gateelectrode 40A, 60A. This field plate is drawn upward out of the trench22B and extends partly above the surface of the semiconductor body 10.The field plate is electrically conductively connected to the gateelectrode 40A and is contact-connected by means of a terminal electrodeG1.

[0054] In one embodiment of the invention, the gate electrode section60A is connected to the gate electrode section 40A, while in anotherembodiment of the invention, provision is made for connecting the twogate electrode sections 40A, 60A to different potentials.

1. A method for fabricating an electrode of a field-effect-controllablesemiconductor component, the method having the following method steps:provision of a semiconductor body (10) having a first zone (12) of afirst conduction type (n) and, arranged above the latter, a second zone(14) of a second conduction type (p), and at least one trench (20A, 20B;22A, 22B) which extends into the semiconductor body (10) in the verticaldirection through the second zone (14), fabrication of a firstinsulation layer (34A, 34B) at least in the region of the second zone inthe at least one trench (20A, 20B; 22A), application of a first layer(40) made of electrode material to the semiconductor body (10),application of an intermediate layer (50) to the first layer (40) madeof electrode material, application of a second layer (60) made ofelectrode material to the intermediate layer (50), removal of the secondlayer (60) made of electrode material and of the intermediate layer(50), the intermediate layer (50) and the second layer (60) made ofelectrode material at least partly remaining in the at least one trench(20A, 20B; 22A, 22B), patterning of the first layer (40) made ofelectrode material (40):
 2. The method as claimed in claim 1, in whichthe semiconductor body has, spaced apart from the at least one trench(20A, 20B; 22A, 22B) in the lateral direction, a third doped zone (16,17, 18) of the second conduction type (p), which is at least partlycovered by a second insulation layer (32).
 3. The method as claimed inclaim 2, in which the intermediate layer (50) and the second layer (60)made of electrode material are removed above the third zone (16, 17,18).
 4. The method as claimed in one of the preceding claims, in which,before the fabrication of the first insulation layer (34A, 34B) in theat least one trench (22A, 22B), a second insulation layer (120A, 120B)is fabricated which at least partly covers the surface of the at leastone trench (22A, 22B).
 5. The method as claimed in claim 4, in which thethird insulation layer (120A) ends below the second zone (14) of thesemiconductor body (10).
 6. The method as claimed in claim 4 or 5, inwhich the fabrication of the third insulation layer (120A) comprises thefollowing method steps: deposition of an insulation layer onto thesemiconductor body (10), removal of the applied insulation layer in theat least one trench (22A) down to a level below the second zone (14) ofthe semiconductor body (10).
 7. The method as claimed in claim 4, inwhich the semiconductor body (10) has at least two trenches (22A, 22B),the second insulation layer (120B) covering the surface of one of thetrenches in the first zone (12) and the second zone (14) of thesemiconductor body (10).
 8. The method as claimed in one of thepreceding claims, in which the second insulation layer (120) is thickerthan the first insulation layer (34A, 34B).
 9. The method as claimed inone of the preceding claims, in which the first layer (40) made ofelectrode material and/or the second layer (60) made of electrodematerial is a semiconductor material, in particular silicon.
 10. Themethod as claimed in one of the preceding claims, in which, during theremoval of the second layer (60) made of electrode material and theintermediate layer (50) firstly the second layer (60) is removed bymeans of an etching method with a stop on the intermediate layer (60)and then the intermediate layer is removed.
 11. Afield-effect-controllable semiconductor component, having the followingfeatures: a semiconductor body (10) having a first zone (12) of a firstconduction type (n), a second zone of a second conduction type (p), andat least one trench which extends into the semiconductor body (10) inthe vertical direction of the semiconductor body (10) through the secondzone (14), a control electrode (40A, 50A, 60A; 40B, 50B, 60B) formed inthe trench, an insulation layer (34A; 34B), which is formed in thetrench and insulates the control electrode (40A, 50A, 60A; 40B, 50B,60B) from the semiconductor body, the control electrode (40A, 50A, 60A;40B, 50B, 60B) has a first electrode section (40A; 40B) adjacent to theinsulation layer (34A; 34B), a second electrode section (60A; 60B) andan intermediate layer (50A; 50B) formed between the first and secondelectrode sections (40A, 50A; 40B, 50B).
 12. The semiconductor componentas claimed in claim 11, in which an insulation layer (120, 120B), whichis thicker than the first insulation layer (34A, 34B) and to which thefirst electrode section (40A, 40B) is applied, is applied in the trenchin the region of the first zone (12) of the semiconductor body (10). 13.The semiconductor component as claimed in one of the preceding claims,which has at least two trenches (22A, 22B), in one of the trenches (22B)the insulation layer (120B) covering the trench (22B) in the region ofthe first and second zones (12, 14) of the semiconductor body (10). 14.The semiconductor component as claimed in one of the preceding claims,in which a field plate (40B), which is insulated from the semiconductorbody (10) by means of an insulation layer (120B) is formed in one of thetrenches (22B), the field plate being electrically conductively.connected to the control electrode (40A, 60A).
 15. The semiconductorcomponent as claimed in claim 14, in which the field plate, insulated bythe insulation layer (120B), runs partly above the semiconductor body(10) and is contact-connected by means of a terminal electrode (G1). 16.The semiconductor component as claimed in one of the preceding claims,in which the first electrode sections (40A, 40B) and the secondelectrode sections (60A, 60B) of the control electrode are connected todifferent potentials.
 17. The semiconductor component as claimed in oneof claims 11 to 16, in which the first electrode sections (40A, 40B) andthe second electrode sections (60A, 60B) of the control electrode areconnected to the same potential.